Hmmm...KR @WOT w/93 Octane and misfires... - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 03-13-2007, 03:42 PM   #1
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Default Hmmm...KR @WOT w/93 Octane and misfires...

!

I am so like out of ideas...

Oil pressure has gone down a little, not loosing any oil or coolant though.

Just doesn't run right... so it'* hard to ignore = /

KR w/93 I guess would mean false knock... but w/ misfires and the KR being applied at only certain times, I just don't think so...

Load is usually around 13-17%, right before or immediately after a shift...

And she seems to be running lean... which is the opposite of what I thought was happening earlier, which was running rich.

I might smell some gas in the vac line from the FPR, but why would that cause a lean condition?

= \
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Old 03-13-2007, 03:46 PM   #2
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How does the O2 look?
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Old 03-13-2007, 04:04 PM   #3
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looks weird...

At cold idle, STFT shifts -7 to +6

At warm idle, STFT shifts -6 to +3, LTFT all over

Driving, STFT more wild, but looks more "normal", LTFT is really all over

As far as what the AutoTap says about the sensors... HOS1 shifts in a not perfectly
smooth pattern from 200 - 800 mv, while HOS2 tends to stay more near 800mv, sometimes completely all over, and sometimes "pegged" at like 750 or 800mv...

Just looking at the trends on a graph gets me confused-- the computer seems really confused about what it wants the engine to do... or something
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Old 03-13-2007, 04:28 PM   #4
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Default Re: Hmmm...KR @WOT w/93 Octane and misfires...

Two things I notice when reading your post:

You mention that fuel pressure is down a little. Has your fuel pump ever been replaced? We know that older pumps begin to fail after a while and at heavy load and WOT, you need all the fuel it can deliver.

You asked about the FPR, which appears to be failing.

IMO, you may have two seperate issues with fuel. Not to mention the possibility of an O2 sensor or CAT issue.
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Old 03-13-2007, 04:46 PM   #5
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--oops

I meant oil pressure... I don't know if fuel pressure has.
A friend gave me one, but it has a short hose, so obviously I can't drive around watching it... and I don't know, would it help watching it at idle?

I could see this being two seperate issues
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Old 03-13-2007, 04:52 PM   #6
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It would certainly help your situation to know what your fuel pressure is at WOT and under load. That'* why idle doesn't usually tell the whole story. I believe that at least one person here got a longer hose so that he could read it in the car while driving...or maybe it was a passenger, I don't know.

In any case, if it were me, I would be replacing that FPR. We know that a failed FPR can cause all kinds of grief and it'* pretty hard to diagnose a system that has other known issues.
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Old 03-13-2007, 05:39 PM   #7
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There can be many causes of KR and not all are false with 93 octane.

Fuel pressure is a large possibility. So are other things, like vacuum and misfires.
I'd be looking at the last tune up and the parts used first, along with fuel pressure before starting to research deeper.

Any other codes besides misfires? Even one occurance could point you in the direction of a possible problem.
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